1. Field of the Invention
The present invention relates to an insole worn between the foot and the shoe of a wearer to provide a comfortable and air-cushioning effect.
2. Description of the Related Art
Insoles or shoe inserts for increasing the comfort of the feet of the wearer have been previously known. Generally, various types of foam and compressionable materials have been utilized with insoles. With many insoles, air is forced from a cushioning material as a wearer walks to provide comfort to a wearer.
U.S. Pat. No. 4,336,661 discloses a shoe insert having an air-impervious envelope and a pad contained therein. The envelope includes a plurality of vent openings throughout its length which release air from the envelope as a wearer walks on the insert.
U.S. Pat. No. 4,571,853 discloses a shoe insert having a plurality of vent openings throughout its length for releasing air as a wearer walks on the insert, wherein the diameter of the vent openings at the heel and toe portions are smaller than the diameter of the vent opening at the arch portion.
U.S. Pat. No. 4,590,689 discloses an insole having vent openings at the heel and toe portions. A foam heelpiece cooperates with the vent openings to meter the escape of air from the insole.
A particular problem of prior art insoles is their tendency to split at the side walls. As a wearer shifts his or her weight on an insole, air is simultaneously moved inside of, released from and drawn into an envelope. Air can become trapped and forced against a side wall until the pressure exceeds the strength of the side wall, causing the side wall to split apart.
The art continues to seek improvements. It is desirable that an insole provide a cushioning and comfortable effect as a wearer walks on it. Furthermore, it is desirable that an insole be durable and long-lasting, and avoid the common problem of splitting at the side walls as found in prior art insoles.